Why are the third and fourth parameters of child.layout() prefixed?

Question

child.layout(x, y, x + child.getMeasuredWidth(), y + child.getMeasuredHeight());

As you can see from the code snippet above, the third parameter is prefixed with x and the fourth with y. Aren't x and y co-ordinates? What's the difference if I do this?

child.layout(x, y, child.getMeasuredWidth(),child.getMeasuredHeight());